Add an application Expert

[Jake-Pullen]

Is your feature request related to a problem? Please describe.
Wouldnt it be cool if Merlin could start applications for you. like steam or web browsers?

Describe the solution you'd like
An application expert with tools that allow for starting applications and maybe also ending applications?

Additional context
will be interesting to see how to handle this system agnostically. initial thoughts seem like we might need two experts, one for linux and one for windows, (screw mac support). Then identify the host system and choose the expert accordingly.